Bertrand Serlet is a very smart guy: you don't get to be in charge of one of the development of one of the principal desktop operating systems (and more to the point, you don't survive Steve Jobs's flamethrower management style) without having a brain something like the size of a planet. In fact he's been working with Jobs since 1989, which means he's come through 22 years where he's held his own with him. This may make Serlet the longest-standing co-worker with Jobs.

Serlet is in the news because of the announcement on Wednesday that he is leaving Apple and his role as senior vice president of Mac software engineering; that job will be taken over by Craig Federighi, who demonstrated the next version of Mac OSX (dubbed "Lion") last October. Federighi, like Serlet, is also an ex-NeXT Computer guy; NeXT was the company Jobs set up after leaving Apple in 1985.

Over at the WSJ's AllThingsD site, John Paczkowski says the departure was a planned transition, with Serlet gradually selling off shares and looking towards doing some sort of academic study. But Serlet's fingerprints are all over core elements of Cocoa, the Objective-C programming language used on Mac OSX.

So Serlet leaves at a time when the rivalries between Microsoft, Apple and Google are growing ever more intense. He's a computer scientist. He's also, as you may have noticed from his name, French.

Which leads us to this example of how there's still some way to go before computers really have everything down pat. The video below shows Serlet poking fun at Vista at Apple's Worldwide Developers Conference in 2006. Pretty standard stuff.

But now go and watch it on YouTube - and turn on the little option (which doesn't come up in the embed) of "Transcribe audio". This uses Google's whizzy speech-to-text system which works on what people say and gives them as subtitles.

However, it's challenged enough when it comes to Steve Jobs: can you guess what it means when it transcribes him saying "But is now called Mr"?

Maybe so. But we think you'll find it more difficult to reverse-engineer this part.

"Two years about doubling the bruce lee, research we've talk a little bit of phone at two fourteen redmond. We're still working on my own home. So we had in the hallways of the conference was the big band of thieves had said 'ride home stalk your foot thick appeals'. Goes on the charge but today it back to you too can seriously."

Puzzled? How about "Off those arena says the backbone saving scrambling to understand how to implement that stuff. Now in terms of fuel values they did the two major innovation. Instead of having is a venue on zip-top arrives."

No? You'll have to go and watch. It is the gift that keeps on giving. Serlet is certainly going to be missed - but the Google Transcribe tool probably won't be among those mourning his departure.

Click this button on YouTube to turn on on-the-fly audio transcription. guardian.co.uk

Remember, to join in the fun, you'll have to watch the video on YouTube, and choose "Transcribe Audio" in the "CC" button, as above.